Precision grinding machine



Nov. 5, 963 A. D. c. STUCKEY- 3,109,263

PRECISION GRINDING MACHINE Filed Nov. 22, 1961 5 Sheets-Sheet l INVENTOR.

ALBERT D. C. STUCKE Y BY ATTORNEYS Nov. 5, 1963 A. D. c. STUCKEY 3, 9

PRECISION GRINDING MACHINE Filed NOV. 22, 1961 5 Sheets-Sheet 2 Nov. 5, 1963 A. D. c. STUCKEY PRECISION GRINDING MACHINE 5 Sheets-Sheet 3 Filed Nov. 22, 1961 Nov. 5, 1963 A. D. c. STUCKEY 3,109,263

PRECISION GRINDING MACHINE Filed Nov. 22, 1961 5 Sheets-Sheet 4 Nov.- 5, 1963 A. D. c. STUCKEY 3,109,263

PRECISION GRINDING MACHINE Filed Nov. 22, 1961 s Sheets-Sheet s In' a 8 m? 1 4w aw? 127 1 m 8 E Q 3 Q V/ 1 Ila-" -i i R o 2 00 an: Y E g? v Ill 44 I2 I VI/A United States Patent Office BylddZhB Patented Nov. 5, 1963 3,109,263 PRECEIQN GRINDING MACHENE Albert D. C. Snickey, incinnati, @hio, assignor to The {Cincinnati Milling Machine Co., Qincinnati, Ohio, a corporation of Ohio Filed Nov. 22, 1961, Ser. No. 154,199 6 Claims. {@i. 51-106) This invention relates to a centertype grinding machine having a feed mechanism which is particularly useful in traverse grinding a workpiece having a stepped surface relation or change in diameter along its length.

An example of a workpiece which has a change in its ground surface diameter is a regulating wheel or roll for a centerless grinding machine used in the grinding of rollers for roller bearings. These regulating wheels are frequently employed with a reduced diameter portion, commonly called a start, at one end. After a period of use, these regulating wheels must be trued and refinished by grinding the peripheral surfaces including the start portion. Since these workpieces are ground on a rather wide cylindrical or barrel surface, a traverse grinding operation is employed for truing whereby a comparatively narrow grinding wheel is caused to move from end to end of the rotating regulating wheel. While the outside diameter of the workpiece may vary from regulating wheel to regulating wheel, it is important that the step between the start and the full diameter of the workpiece remains the same. To preserve the proper step on the workpiece, the operator of the roll grinding machine must make frequent measurements and adjustments or" his machine. These adjustments require considerable time and result in increased costs for the truing operation.

it is therefore an object of this invention to provide a feed mechanism in a grinding machine which will facilitate the grinding of a workpiece from end to end including a stepped diameter portion without requiring an adjustment by the machine operator at the step between a reduced diameter and a larger diameter of the workpiece.

Another object is to provide a grinding machine with a feed mechanism which will maintain accurately a similar step relationship between diameters of workpieces in repeated grinding operations without an operators measuring the workpieces and adjusting of the machine at each stepped portion.

Still another object of this invention is to provide a feed mechanism which includes a plurality of independently operable means to rotate a single feed drive shaft without the use of clutches to isolate the means from one another.

A further object of this invention is to provide a machine which will reduce the cost of grinding a batch of workpieces having stepped diameters by reducing the time required for the correct grinding of each workpiece.

Other obiects and advantages of the present invention should be readily apparent by reference to the following specification, considered in conjunction with the accompanying drawings forming a part thereof, and it is to be understood that any modifications may be made in the exact structural details there shown and described, within the scope of the appended claims, without departing from or exceeding the spirit of the invention.

A grinding machine having a feed mechanism constructed in accordance with the preferred form of this invention utilizes a rack and pinion drive to move the wheelhead toward and away from a workpiece. The rack is fixed to the wheelhead and the pinion is fixed on a drive shaft that is rotatably supported in the machine base. .The drive shaft is reversely rotatable by selected operation of each of three mechanisms without the use of isolation clutches to provide movement of the wheelhead either toward or away from the workpiece.

One of the three mechanisms is a rapid traverse motor of the fixed angular stroke type. This motor is supported on the drive shaft and has a paddle rotor which is rotatable a limited amount with the drive shaft within the motor housing. The limited amount of rotation of the paddle and shaft defines the fixed angular stroke when the motor is operated. The entire motor unit, including the housing and rotor, and drive shaft are rotatable together in the base. A worm wheel is integral with the rapid advance motor and it is engaged by a worm gear. The worm gear is supported in the base for rotation and for axial movement. The worm gear is utilized to create a restaining force on the rapid advance motor housing when that motor is energized to rotate the drive shaft through the fixed angular stroke. This force causes the drive shaft to be rotated relative to the base while the rapid advance motor housing is held stationary and when the rapid advance motor is operated. The wheelhead is moved a fixed distance thereby.

When the rapid advance motor has been operated to move the drive shaft and paddle to one or the other of the extreme angular positions within the rapid advance motor housing, the rapid advance motor housing and paddle and the drive shaft become relatively rigid to act as a single unit due to forces created within the motor. Therefore, rotation of the worm gear will cause the drive shaft to rotate and move the wheelhead. A handwheel mechanism is connected to the worm gear and is utilized to produce a selected rotation thercof. The handwheel mechanism then furnishes a second means to rotate the drive shaft and produce movement of the wheelhead.

The linkage between the handwheel and worm gear contains a sliding coupling in which a yieldable bias force is created tending to push the worm gear axially in one direction. A mechanism is included in the base which stops movement of the worm gear in the one direction and includes a piston and cylinder motor which is operable to produce a force on the worm gear which will overcome the bias force and move the Worm gear in the other direction. When moved, the worm gear acts as a rack and the worm wheel acts as a pinion. Operation of the piston and cylinder motor then is a third mechanism by which the wheelhead'may be moved.

The operation of the piston and cylinder motor is controlled by a tracer mechanism contained on the base and engaged with a cam fixed to the movable table on which the workpiece is supported and by which the workpiece is passed across the cutting periphery of the grinding wheel. The cam is contoured either to cause the piston and cylinder motor to push the worm in one direction or to allow the bias force to move the worm in the other direction depending upon the desired movement of the wheelhead. Thus the cam may be properly shaped and positioned on the table to effect movement of the wheelhead to grind from one diameter to another automatically and accurately without a manual machine adjustment. I

.A complete understanding of the construction and operation of this invention may be obtained from the following detailed description in which reference is made to the attached drawings wherein:

FIG. 1 is a plan view of a grinding machine.

FIG. 2 'is a side elevation of the grinding machine shown in FIG. 1 from the left side.

FIG. 3 is a partial front elevation of the grinding machine shown in FIGS. 1 and 2.

FIG. 4 is a sectional view of a hydraulic control mechanism on the same plane as FIG. 5.

FIG. 5 is a sectional view of a portion of the machine on line 5-5 of FIG. 3. Y

7 FIG. 6 is a sectional view of a hydraulic motor shown in FIG. 3 on line 6- 6. g The grinding machine shown in FIGS. 1 and 2 in which 3 the present invention is incorporated is a modified centertype grinding machine having a wheelhead mounted on ways 12-, 14 (FIG. 3) in an intermediate member 16 for reciprocal movement thereon by mechanism to be described subsequently. The intermediate member 16 is pivotally adjustable on the base 18 of the machine. The wheelhead includes a grinding wheel 26 rotatable by operation of a motor 22 mounted on an upper portion 23 of the wheelhead 10. A truing mechanism 24- is mounted on the wlieelguard 26 behind the grinding Wheel 20. (The truing mechanism 24 is not shown in FIG. 1 for simplicity.) The wheel guard 26 extends from the side of the upper portion 28 of the wheelhead 16. The grinding wheel 29, motor 22, wheelguard 26, and truing mechanism are all received on and move with the upper portion 28 of the wheelhead 10, FIGS. 2 and 3. The upper portion 28 is pivotally adjustable on a horizontal axis through yokes 39 on the lower portion 32 of the wheelhead 19. As shown in FIG. 3, the yoke 3% extends laterally from the left side of the lower portion 32. A hinge shaft 31 extends through the yoke 31 to provide the surface on which the upper portion 23 moves when it'is pivotally adjusted on the horizontal axis. Thus the grinding wheel 2% may be tilted for grinding a helical groove or lead or a workpiece, the adjustment being accomplished by the unclamping and reclamping of the portion 23 relative to the lower portion 32 by stud bolts 33, 34, 35 (FIG. 3).

workpieces to be ground are rotatably supported on the table 36 which is received on the base 13 for movement along its longitudinal axis. A fixture 38 is pivotally mounted on the table 35. The fixture 38 is adapted to support the entire regulating wheel housing of a centerless grinding machine such that the regulating wheel therein is positioned as indicated in phantom at 39. A regulating wheel housing is clamped directly to the fixture 33 during the grinding operation. A motor 42 and drive unit 44 are also supported on the table and furnish the power to rotate the regulating wheel in the fixture 33 during the grinding operation. A front handwheel 46 and a rear handwheel 48 are mechanically connected for manual movement of the table 36.

A bracket 56 is fixed to the side of the table 36 and is adapted to hold a cam 52 for engagement by a hydraulic tracing mechanism 54 which is fixed to the base 18 below the wheelhead' 10. The hydraulic tracing mechanism is connected for movement of the wheelhead 10 on the base 18 in accordance with the contour of the cam 52 and the movement of the table 36.

The wheelhead 10 is moved on the ways 12, 14 in the intermediate member 16 by rotation of a pinion 56 which is fixed on the end of a drive shaft 58 and engaged with arack 66. The rack 66 is fixed to. the underside of the lower portion 32 of the wheelhead 1t) and is parallel to the ways 12, 14. The shaft 58 is journaled for rotation in the base 18 on the axis about which the intermediate member 16 is pivotally adjustable. Supported on the shaft 58 for rotation therewith is a rapid advance motor 62 which has a worm wheel 64 integral therewith. As shown in FIG. 6, the motor 62 is a fixed rotary stroke motor comprising an annular housing 66 with an inwardly extending wall member 68 fixed therein and a paddle 70 fixed to the drive shaft 58. Interdrilling 72, 74 in the shaft 58 is adapted to supply fluid under pressure to one side or the other of the paddle 70 to cause it to swing from one side to the other of the wall 68. Thus the housing 66 and shaft 58 are relatively rotatable an amount equal to the arcuate swing of the paddle 79 in moving from engagement with one side of the wall 68 to engagement with the other side. By furnishing means to hold the housing 66 stationary, the shaft 58 may be rotated in the machine base 18 to effect a fixed amount of rapid movement of the wheelhead 10 toward or away from the table 36.

As shown in FIG. 5, the housing ti may be held fixed within the base 18 by the engagement of the worm wheel 64 with a worm gear 76 which is integral with a shaft 78 that is journaled for rotation in an inner portion 86 of the base 18. The shaft 78 is received in the base por} tion fill for limited axial movement. A cylinder defined by the bushing 82 and closed by the cap 84 is received in the base portion 3d and supplied with fluid under pressure through the fluid conduit 86 at the left side of a piston member 88. The piston 88 is fixed on the shaft 78. The piston 88 and cylinder 82 urge the shaft 78 toward its extreme rightward position as viewed in FIG. 5.

The extreme rightward position of the shaft 78 is limited by a pin 90 which engages the end of the shaft '78. The pin is fixed in the end of a slide member 92, FIG. 4, which is received through a member 94. The member 94 is fixed to the side of the base 18 below the wheelhead 1t and is the member on which the hydraulic tracing mechanism is supported. A pin 96 extends through a side member d3 which, with the member 94, defines a slide way of rectangular cross section. The pin 96 extends into a short slot 1% in the slide member 92 and limits the extremes of movement of the slide member 2. A roller 1 32 is received on a pin 104 fixed in the slide member @2 and is forced against an inclined cam 1% by the bias force created in the cylinder bushing 32 on the piston 88 (FIG. 5). The cam 106 is fixed in a bracket 163 which in turn is fixed to the body 110 of a reciprocally movable tracing valve 112. Thus, by shifting the cam 186 one way and the other, the slide 92 may be moved to change the extreme rightward position of the shaft 73 as viewed in FIG. 5. When the shaft '78 is axially moved, the worm 76 acts as a rack and the worm wheel 64- acts as a pinion and the entire motor 62 together with the shaft 58 is rotated to move the wheelhead 10. This is movement of the wheelhead 10 that is independent of operation of the motor 62.

The tracing valve 112 is composed of the body It? in which a valve bushing 11% is received. The bushing 114 has five portions including a pressure port 116 at its center and return ports 118, 120 at each end. Between the pressure and return ports 118, 116, 120 are operating ports 122, 124. A plunger 126 is slidably received in the bushing 1114 and has lands 12-6, 130, .132 spaced such that when axially centered in the bushing 114 the pressure port 116 and return ports 1'13, 126' are all just closed and there is no fluid flow from the pressure port 116 to either of the operating ports 122, 124. A stem 134 extends from the plunger 126 through a spring 136 which is compressed between collars 138, 140. The collar 138 is fixed in an end member 142 that is fixed to and extends from the body 110. The collar is fixed on the stem 134. The spring 136 then tends to cause the plunger 126 to move to the right end of the bushing 114, as viewed in FIG. 4, to connect pressure from port 116 to operating port 122 while the return port 120 is connected to operating port 124.

The plunger 126 may be moved against the force created by the spring 136 to connect pressure port 116 to port 124 and return port 118 to port 122. This is accomplished by shifting a tracing plunger 144 which is axially movable in the end member 142 on balls 146 in cage 148. One end of the tracing plunger 144 engages the end of the stem 134 while the other end holds a tracing nib 150 which is adapted to engage the cam 52 (FIG. 1) fixed on the table 36. 1

Another end member 152 extends from the opposite end of the valve body 110. The end member 152 is received slidably through a bushing 154 which is fixed on the left end of the tracing housing 156 that encloses the tracing valve 112. A cylinder member 158 is fixed to the bushing 154 and is closed by a cap 16%. On the end of the member .152 are fixed a pair of discs 162, 164 which carry piston rings 165 and define a piston in the cylinder 158. An interdrilled fluid passage 166 connects the operating port 122 to the left side of the piston 162, 164 and a second interdrilled fluid passage 168 connects the operating port 124 to the right side of the piston 162, 164, as vie-wed in FIG. 4.

Since the plunger 126 in the valve 112 is normally caused to connect pressure port 115 to port 122, passage 166 connects pressure to the left of the piston 162, 164. The right side of the piston 162, 164 connects to return for the same reason through passage 16:; which connects through port 124 to return port 121). The piston 162, 164 is forced into engagement with the end bushing 154 and the valve 112 is carried to a corresponding position since the end members 152 and 142 and the valve body 111 are all fixed together and the end member 142 is slidably received through a bushing 17% fixed to the housing 156. This causes the cam 106, which moves with the valve body 115 to assume a predetermined position relative to the slide member 92 and the shaft 78 moves to assume a corresponding axial position.

Engagement of the cam 52 (FIG. 1) by the nib 156 causes a shift of the plunger 144 to a predetermined position dependent upon the surface of the cam 52 causing in turn a shift of the valve plunger 126 to reverse the pressure and return connections to the cylinder 153. The valve body 11% and valve bushing 114 are carried back relative to the valve plunger 126 by the piston 162, res to a position where the fluid connections to the cylinder 153 on each side of the piston 162, 164 create forces thereon to equalize the forces transmitted to the valve 112 from the spring 135 and the piston 88 (FIG. 5). The plunger 126 is positioned in the valve bushing 114 such that the land 13?; wouid be approximately centered over the pressure port 116. Thus further movement of the wheelhead 1% is stopped until another change in the contour of the cam 52 is brought into engagement with the nib 159. Thus the valve body 111) to which the cam 1% is fixed would be caused to follow the changes in axial position of the tracer plunger 144 and the shape of the cam 52 (FIG. 1) will determine the position of the tracer plunger 144 as the table 36 is moved across the peripheral surface of the grinding wheel 21). The position of the cam 1% determines the axial position of the shaft 78 (FIG. 5) and changes in its position result in changes in position of the wheelhead 113 on the ways 12, 14 (FIG. 3) due to the operation of the worm gear 7 6 and worm wheel od. The tracing mechanism 54 then is another means for effecting movement of the wheelread 1%, the movement effected being a predetermined amount in response to movement of the table 35.

Another means for effecting a selected movement of the wheelhead 1ft (FIGS. 1 and 2) is by rotation ofthe handwheel 172 which is connected to rotate the gear 174-, shown in FIG. 5. The gear 174 is fixed to a shaft 176 which is journaled for rotation in the base 1%. A coupling member 178 is fixed on one end of he shaft 176 and has a slot 18% extending along one side. The slot 139 is slid-ably engaged with a tongue 182 of a mating coupling member 184 which is fixed to the end of the shaft 78. The shafts 78 and 175 are in alignment but are separated by a space to allow for the axial movement of the shaft '73 by the tracing mechanism 54. The mating coupling elements 173, 134 render the two shafts 7'8, 75 rotatable together while they remain relatively movable axially. Therefore, by rotating the handwheel 172, the Worm gear 76 may be rotated to rotate the worm wheel 4 and rapid advance motor 62 as a unit, including the housing 5-6 and paddle '7 8, together with the drive shaft 53.

From the foregoing description it is evident that the wheelhead 1% may be moved by one of three means including the rapid advance motor 62 (FIG. 3), the handwheel 1'72 (ET-GS. 1, 2) and the tracing mechanism 54 (FIGS. 1, 4). ach of the three may be operated independently of the others and all result in a rotation of the drive shaft 53 (FIG. 3) to which the pinion 56 is fixed.

What is claimed is:

1. A grinding machine comprising in combination, a base structure, a worktable reciprocally movable on said base structure and adapted to support a workpiece during a grinding operation, a wheelhead having a rotatable grinding wheel carried thereby slidably received on said base structure for movement toward and away from said worktable, a fixed rotary stroke rapid advance motor unit selectively operable to move the wheelhead toward and away from the worktable a fixed distance, a handwheel mechanism operable to rotate said rapid advance motor unit to effect movement of said 'wheelhead a selected distance toward and away from said worktable and including a yieldably supported member therein, a hydraulic motor operable to shift said yieldably supported member to rotate said rapid advance motor unit to produce movement of said wheelhead independently of said handwheel mechanism, a cam fixed to said worktable, and a following mechanism attached to said base structure, engaged with said cam, and operable to control the connection of fluid under pressure to said hydraulic motor, said following mechanism and cam effective to operate said hydraulic motor to produce a predetermined movement of said wheelhead in response to a predetermined movement of said worktable.

2. A grinding machine comprising in combination, a base structure, a work-table reciprocally movable on said base structure and adapted to suppont a workpiece during a grinding operation, a wheelhead having a rotatable grinding wheel carried thereby slidably re ceived on said base structure for movement toward and away from said worktable, a rack fixed to said wheelhead and in line with the direction of movement thereof, a drive shaft rotatably supponted in said base and having a worm wheel and a pinion thereon, said pinion engaged with said rack, a rotatably and axially movable worm gear engaged with said worm wheel, bias means tending to hold said worm gear in a predetermined location, means to rotate said worm gear to effect selected movement of said wheelhead on said base struc- 'ture, hydraulic motor means operable in one direction to overcome said bias means and to axially move said worm gear to effect movement of said wheelhead in one direction and operable in the other direction to yield before said bias means ltO produce movement of said wheelhead in the other direction, a cam fixed to said worktable, and a following mechanism fixed to said base structure, engaged with said cam, and operable to control the connection of fluid under pressure to said motor means, said following mechanism and cam effective to operate said motor means to produce a predetermined movement of said wheelhead in response to a predetermined movement of said worktable.

3. A grinding machine comprising in combination, a base structure, a table member slidably received on said base structure and adapted to suppont a workpiece for movement along a predetermined path, a wheelhead having a rotatable grinding wheel carried thereby slidably received on said base structure for movement toward and away from said predetermined path, a rack fixed to said 'wheelhead, a fixed rotary stroke rapid advance motor rotatably supported in said base structure and having a worm wheel fixed thereto and a 'drive shaft extending therefrom, said drive shaft rotated by said rapid advance motor when said rapid advance motor is operated and rotated therewith when said rapid advance motor is rotated, a pinion fixe -d to said drive shaft and engaged with said rack for movement of said wheelhead when said pinion is rotated, a Worm gear engaged with said worm wheel and supported in said base structure for rotational and axial movement, said worm gear effective to prevent rotation of said rapid advance motor when amazes said rapid advance motor is operated and said worm gear is held axially stationary to effect a fixed rotation of said pinion, a handwheel mechanism to rotate said Worm gear to produce a selected rotation of said rapid advance motor and pinion, said handwheel mechanism including bias means tending to maintain said worm gear in a predetermined axial location, a hydraulic motor selectively operable to overcome said bias means and shift said worm gear from said axial location to produce a predetermined rotation of said rapid advance motor and pinion, and means responsive to predetermined movement of said table member to operate said hydraulic motor.

4-. A grinding machine comprising in combination, a base structure, a table member slidably received on said base structure and adapted to support a workpiece for movement along a predetermined path, a wheelhead having a rotatable grinding wheel carried thereby slidably received on said base structure for movement toward and away from said predetermined path, a rack fixed to said Wheelhead, a fixed rotary stroke rapid advance motor rotatably supported in said base structure and having a worm wheel fixed thereto and a drive shaft extending therefrom, said drive shaft rotated by said rapid advance motor when said rapid advance motor is operated and rotated therewith when said rapid advance motor is rotated, a pinion fixed to said drive shaft and engaged with said rack for movement of said Wheelhead when said pinion is rotated, a Worm gear engaged with said worm :wheel and supported in said base structure for rotational and axial movement, said worm gear efiec- \tive to prevent rotation of said rapid advance motor when said rapid advance motor is operated and said worm gear is held axially stationary to effect a fixed rotation of said pinion, a handwheel mechanism to rotate said worm gear to produce a selected rotation of said rapid advance motor and pinion, said handwheel mechanism including bias means tending to maintain said worm gear in a predetermined axial location, a hydraulic motor selectively operable to overcome said bias means and shift said worm gear from said axial location to produce a predetermined rotation of said rapid advance motor and pinion, "a cam fixed to said table member and movable therewith, a hydraulic tracing mechanism supported on said base structure and engaged with said cam, said tracing mechanism operable to energize said hydraulic motor to produce a predetermined rotation of said rapid advance motor and pinion thereby.

5. A grinding machine comprising in combination, a base structure, a worktable reciprocally movable on said base structure and adapted to support a workpiece during a grinding operation, a Wheelhead having a rotatable grinding wheel-carried thereby slidably received on said base structure for movement toward and away from said worktable, a rack fixed to said wheelhead and extending parallel to the direction of movement thereof, a drive shaft rotatably received in said base structure, a pinion fixed on said drive shaft and engaged with said rack,

a drive mechanism including a pair of relatively axially movable members rotatable together and bias means to tend to shift one member in one direction to a predetermined position relative to the other member, a motor connected to said drive mechanism and operable to overcome said bias means and shift said one member in the other direction, means to operate said motor a predetermined amount in response to movement of said worktabl-e, and means connected between said drive shaft and drive mechanism for rotation of said drive shaft in response to both axial and rotational movement of said one member.

6. The grinding machine comprising in combination, a base structure, a worktable reciprocally movable on said base structure and adapted to support a workpiece during a grinding operation, a wheelhead having a rotatable grinding wheel carried thereby slidably received on said base structure for movement toward and away from said worktable, a rack fixed to said wheelhead and extending parallel to the direction of movement thereof, a drive shaft rotatably received in said base structure, a pinion fixed on said drive shaft and engaged with said rack, a;

worm wheel fixed on said drive shaft, a handwheel shaft rotatably suported in said base structure, an axially and rotatably movable shaft aligned with said handwheel shaft and having a worm integral therewith engaged with said worm wheel, an axially sliding coupling received between said handwheel and worm shafts for the transmission of rotational forces therebetween, a piston fixed to said worm shaft, a cylinder in said base structure receiving said piston, means to connect fluid under pressure to one side of said piston for creation of a bias force tending to move said worm shaft in one direction to a predetermined position relative to said handwheel shaft, a motor connected to said worm shaft for shifting said worm shaft against said bias force when operated in one direction and for allowing said bias force to shift said Worm shaft toward said predetermined position when operated in the other direction, a cam fixed to said worktable, and a tracing mechanism supported on said base structure and connected to control the operation of said motor one way and the other in accordance with the contour of said cam when said worktable is reciprocated.

References Cited in the file of this patent UNITED STATES PATENTS 909,895 Hanson Jan. 19, 1909 991,345 Mitchel May 2, 1911 2,241,634 Decker May 13, 1941 2,646,651 Wilson July 28, 1953 2,803,095 Monica Aug. 20, 1957 FORElGN PATENTS 645,409 Germany May 28, 1937 

1. A GRINDING MACHINE COMPRISING IN COMBINATION, A BASE STRUCTURE, A WORKTABLE RECIPROCALLY MOVABLE ON SAID BASE STRUCTURE AND ADAPTED TO SUPPORT A WORKPIECE DURING A GRINDING OPERATION, A WHEELHEAD HAVING A ROTATABLE GRINDING WHEEL CARRIED THEREBY SLIDABLY RECEIVED ON SAID BASE STRUCTURE FOR MOVEMENT TOWARD AND AWAY FROM SAID WORKTABLE, A FIXED ROTARY STROKE RAPID ADVANCE MOTOR UNIT SELECTIVELY OPERABLE TO MOVE THE WHEELHEAD TOWARD AND AWAY FROM THE WORKTABLE A FIXED DISTANCE, A HANDWHEEL MECHANISM OPERABLE TO ROTATE SAID RAPID ADVANCE MOTOR UNIT TO EFFECT MOVEMENT OF SAID WHEELHEAD A SELECTED DISTANCE TOWARD AND AWAY FROM SAID WORKTABLE AND INCLUDING A YIELDABLY SUPPORTED MEMBER THEREIN, A HYDRAULIC MOTOR OPERABBLE TO SHIDT SAID YIELDABLY SUPPORTED MEMBER TO ROTATE SAID RAPID ADVANCE MOTOR UNIT TO PRODUCE MOVEMENT OF SAID WHEELHEAD INDEPENDENTLY OF SAID HANDWHELL MECHANISM, A CAM FIXED TO SAID WORKTABLE, AND A FOLLOWING MECHANISM ATTACHED TO SAID BASE STRUCTURE, ENGAGED WITH SAID CAM, AND OPERABLE TO CONTROL THE CONNECTION OF FLUID UNDER PRESSURE TO SAID HYDRAULIC MOTOR, SAID FOLLOWING MECHANISM AND CAM EFFECTIVE TO OPERATE SAID HYDRAULIC MOTOR TO PRODUCE A PREDETERMINED MOVEMENT OF SAID WHEELHEAD IN RESPONSE TO A PREDETERMINED MOVEMENT OF SAID WORKTABLE. 